King County’s noxious weed program tackles several high priority species in April

King County’s noxious weed specialists have their hands full this month and it isn’t going to get easier anytime soon. Top priority noxious weeds they are focusing on this month include garlic mustard, European coltsfoot, giant hogweed and shiny geranium. Other regulated noxious weeds that are following close behind are spotted knapweed, wild chervil and sulfur cinquefoil. And that’s just the short list of priority species that are regulated under Washington’s state noxious weed law.

Garlic mustard is probably the most challenging species we are chasing this month. It is a Class A noxious weed so we are trying to find and eliminate every plant, but it is one of the most difficult plants to locate.

garlic mustard starting to flower in early April

Garlic mustard is starting to flower in April so it is easier to find, but also starts the clock on controlling it before it goes to seed. Photo by Karen Peterson.

This month garlic mustard is producing taller, flowering stems, so it will be easier to find. But it also means the clock is ticking if we are going to control all the plants before they set seed.

garlic mustard in early April with flower buds

In early April, garlic mustard gets taller and starts to form flower buds in tight clusters on tops of stems. Photo by Karen Peterson.

patch of garlic mustard seedlings in early April

April is also when garlic mustard seedlings are popping up in huge numbers. Photo by Karen Peterson.

Large patch of garlic mustard

Large patches of garlic mustard can be a challenge to control. Photo by Karen Peterson.

In large, forested areas like Coal Creek Natural Area, garlic mustard has a tendency to blend in among look-alike forest plants like nettles and fringe cup. Along waterways such as the Cedar River and Big Soos Creek or steep hillsides like the forests of Golden Gardens and Carkeek Parks, the terrain is another challenge, making it difficult to even get to the plants to control them.

garlic mustard on hill

Garlic mustard is often found on steep hillsides like this patch in Carkeek Park. Photo by Karen Peterson.

We have contacted property owners and asked for access to survey and control garlic mustard. It will be a big help if anyone receiving a request responds quickly so we have more time to get to all the properties. In King County, anyone who has garlic mustard on their property can contact our office and we will come and control it. Stopping garlic mustard from spreading is just that important!

Another scary plant for us is European coltsfoot (see feature article in this blog), just added to the noxious weed list in 2018. This month is the perfect time to look for the plant because both the leaves and the flowering stems are visible in most cases. The flowers are starting to fade and form seeds though, so we need to act quickly to prevent spread.

Flowers and leaves of European coltsfoot

In April, both flowering stems and new leaves are visible on European coltsfoot (Tussilago farfara). Photo by Tricia MacLaren.

new leaves of European coltsfoot

New leaves of European coltsfoot emerge in April, followed by new rhizome growth. Photo by Tricia MacLaren.

This year’s rhizomes will start to grow also, so this is a great month to control European coltsfoot no matter what method you use. Because this plant is so brand new for us, we are still learning the best way to control it. If you have experience with controlling this plant, we’d love to hear from you.

European coltsfoot is often spread by fragments of rhizomes carried by water and soil erosion, but also carried in contaminated rock and gravel materials. We have found it growing in places near construction, in gravel piles and along waterways.

European coltsfoot emerging from a rock crevice.

European coltsfoot can be spread by root fragments in rock material and gravel. Photo by Matt Below.

Workers looking at European coltsfoot patch

This large patch of European coltsfoot was found this spring near the Highway 520 bridge. Photo by Tricia MacLaren.

Shiny geranium is also in full force right now. We are finding an alarming number of new locations, some of which are quite large.

shiny-geranium-large-patch-Minwook-truck-04062018-MWinkler

Large dense patches of shiny geranium like this one on Vashon Island show just how invasive this plant can be. Photo by Maria Winkler.

shiny-geranium-solid-patch-boot-04062018-MWinkler

Where shiny geranium grows, there’s not much room for anything else to grow. Photo by Maria Winkler.

Even though this plant doesn’t seem that bad – it’s small and not even poisonous – people who have dealt with it in Oregon have warned us just how invasive and pervasive it can be. Probably we are at the point where we still have an opportunity to keep it from establishing everywhere, but it’s a small window that is closely quickly. Please can help by looking for and reporting shiny geranium whenever they see it.

shiny-geranium-roadside-infestation-Vashon-04062018-MWinkler

Shiny geranium carpets open disturbed areas first, but then can work its way into less disturbed areas. Photo by Maria Winkler.

shiny-geranium-tree-Minwook-04062018-MWinkler

Shiny geranium can be found in all sorts of nooks and crannies. Photo by Maria Winkler.

Giant hogweed is still just emerging this month and won’t start flowering for another couple of months, but it is so conspicuous that we can usually spot it even when it’s small.

giant hogweed plant

Giant hogweed leaves start to get really large in April and stems are distinctive with their purple spots and stiff white hairs. Photo by Brian Wingert.

hogweed stems with seedlings emerging below

Different aged giant hogweed plants can often be found at the same location, with new seedlings emerging below older plants. Photo by Sasha Shaw.

hogweed plants by tree

Giant hogweed is most often found near residential areas but in out of the way places where it has been overlooked. Photo by Sasha Shaw.

Hogweed sap makes skin hyper-sensitive to sunlight and often causes burns and blisters to anyone who is unlucky enough to come in contact with it. Gloves, long sleeves and eye protection are highly recommended when controlling hogweed plants. Young plants can be dug up but make sure to get the whole root. Here in King County, please let us know if you see any hogweed so we can work on getting rid of it before anyone gets burned.

hogweed plant by shovel

Giant hogweed is very conspicuous in April. It is also small enough to be controlled easily by digging. Photo by Karen Peterson.

county worker standing by hogweed plants

King County weed specialists can help homeowners remove their giant hogweed if they aren’t able to do it. Photo by Sarah Baker.

Here are a few more regulated noxious weeds King County staff are targeting this month.

Spotted knapweed
The most abundant of the knapweed species on the noxious weed list, spotted knapweed gets taller this month and can be easier to find. The leaves are grayish-green and deeply lobed and old brown flower stems from last year might still be visible. This plant is most common in really gravelly, well-drained soils like you might find on a roadside, railroad edge or along some riverbanks and gravel bars.

spotted knapweed plant in April with old stems

Spotted knapweed starts to grow taller in early April. Old flower stalks often remain to show how much taller the plant will grow. Photo by Dan Sorensen.

spotted knapweed plants in grassy field in April

Spotted knapweed is often found in areas with a lot of soil disturbance and not much competitive grass cover. Photo by Dan Sorensen.

Wild chervil
This relative of parsley and carrot is not as scary as poison-hemlock or as tall, but it is very invasive and can be tough to get rid of (see feature article in this blog). Most of the large infestations in King County are in the area between Enumclaw and Auburn, but it is possible that other populations have escaped notice. Identification can be difficult, so it’s best to get an expert opinion on this one. Look for small white flowers, stems that are entirely green and ribbed or furrowed, leaves that are highly dissected, and plants that are about two to three feet tall when in flower.

wild chervil plant

Wild chervil starts to flower in April. It looks similar to other plants in the same family so expert identification is a good idea. Photo by Dan Sorensen.

wild chervil growing in the woods

Large, dense patches of wild chervil can be challenging to control, especially in rough terrain like this. Photo by Dan Sorensen.

Sulfur cinquefoil
Sulfur cinquefoil is another noxious weed that can escape notice until it completely takes over. The leaves are distinctive with their 5 to 7 toothed lobes that resemble a hand. However, the leaf color blends with the grass it usually grows with and the pale yellow flowers are not that much help either. Once it gets established, sulfur cinquefoil can crowd out even grass as it forms a dense monoculture. We find this plant all over the county, but it is most troublesome in areas with low-nutrient, rocky soils where it has a big advantage over grass and other plants.

sulfur cinquefoil plant emerging in April

Sulfur cinquefoil starts to grow larger in April and can be easier to find. Photo by Dan Sorensen.

seed capsules of sulfur cinquefoil

In April, last year’s seed capsules of sulfur cinquefoil can still be found, but the tiny seeds have mostly dispersed already. Photo by Dan Sorensen.

For the whole list of noxious weeds we are looking for, check out the King County Noxious Weed List. Species that are regulated are on the top of the list, either Class A, B or C regulated species. Property owners (and that includes public agencies like ours) are required by our state noxious weed law to control these species to prevent them from spreading further.

In many cases, we can help property owners control their regulated species, especially Class A noxious weeds that are the highest priority, so make sure to get in touch if you are having trouble tackling your noxious weeds. Also, King County residents can help us by reporting locations of regulated noxious weeds on our online reporting form or by contacting us.



Categories: Program News, Tips, Weed Control, Weed Identification

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